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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1960

Free-spinning-tunnel Investigation of a 1/30 Scale Model of a Twin-jet-swept-wing Fighter Airplane

An investigation has been made in the Langley 20-foot free-spinning tunnel to determine the erect and inverted spin and recovery characteristics of a 1/30-scale dynamic model of a twin-jet swept-wing fighter airplane. The model results indicate that the optimum erect spin recovery technique determined (simultaneous rudder reversal to full against the spin and aileron deflection to full with the spin) will provide satisfactory recovery from steep-type spins obtained on the airplane. It is considered that the air-plane will not readily enter flat-type spins, also indicated as possible by the model tests, but developed-spin conditions should be avoided in as much as the optimum recovery procedure may not provide satisfactory recovery if the airplane encounters a flat-type developed spin. Satisfactory recovery from inverted spins will be obtained on the airplane by neutralization of all controls. A 30-foot- diameter (laid-out-flat) stable tail parachute having a drag coefficient of 0.67 and a towline length of 27.5 feet will be satisfactory for emergency spin recovery.

Bowman, James S., Jr.↗
NASA NTRS1983

Surface analyses of carbon fibers produced from polyacrylonitrile fibers at low carbonization temperatures

A process for producing carbon fibers from polyacrylonitrile at low carbonization temperatures was studied. The bulk and surface properties of fibers obtained after reaction with benzoic acid, air and carbonizing in nitrogen or a dilute acetylene atmosphere are discussed. All fiber products had different surface and internal compositions. Samples produced at temperatures up to 950 C and carbonized in nitrogen contained substantial quantities of nitrogen and oxygen at the surface. During carbonization, the surface nitrogen converted into two new forms, possibly nitrile and an azo or a new carbon-nitrogen bond. Samples carbonized in acetylene contained a carbon-rich surface stable to oxidation.

Cagliostro, D. E.↗
NASA NTRS1990

Potential technology transfers of research on low-temperature carbon monoxide-oxygen recombination catalysts

Results from research on catalytic recombination of CO-O2 for stable closed-cycle operation of CO2 lasers hold much promise for a variety of technology transfer. Expansion of CO2 laser remote sensing applications toward chemical detection and pollution monitoring would certainly be expected. However, the catalysts themselves may be especially effective in low-temperature oxidation of a number of chemicals in addition to CO. It is therefore of interest to compare the CO-O2 catalysts with chemical systems designed for chemical sensing, air purification and process catalysis. Success in understanding the catalytic mechanisms of the recombination of CO-O2 could help to shed light on how catalyst systems operate. New directions in low-temperature oxidation catalysts, coatings for chemical sensors and sorbents for air purification could well emerge.

Poziomek, Edward J.↗
NASA NTRS1996

Buoyancy-Driven Heat Transfer During Application of a Thermal Gradient for the Study of Vapor Deposition at Low Pressure Using and Ideal Gas

A mathematical model has been developed to determine heat transfer during vapor deposition of source materials under a variety of orientations relative to gravitational accelerations. The model demonstrates that convection can occur at total pressures as low as 10-2 mm Hg. Through numerical computation, using physical material parameters of air, a series of time steps demonstrates the development of flow and temperature profiles during the course of vapor deposition. These computations show that in unit gravity vapor deposition occurs by transport through a fairly complicated circulating flow pattern when applying heat to the bottom of the vessel with parallel orientation with respect to the gravity vector. The model material parameters for air predict the effect of kinematic viscosity to be of the same order as thermal diffusivity, which is the case for Prandtl number approx. 1 fluids. Qualitative agreement between experiment and the model indicates that 6-(2-methyl-4-nitroanilino)-2,4-hexadiyn-l-ol (DAMNA) at these pressures indeed approximates an ideal gas at the experiment temperatures, and may validate the use of air physical constants. It is apparent that complicated nonuniform temperature distribution in the vapor could dramatically affect the homogeneity, orientation, and quality of deposited films. The experimental test i's a qualitative comparison of film thickness using ultraviolet-visible spectroscopy on films generated in appropriately oriented vapor deposition cells. In the case where heating of the reaction vessel occurs from the top, deposition of vapor does not normally occur by convection due to a stable stratified medium. When vapor deposition occurs in vessels heated at the bottom, but oriented relative to the gravity vector between these two extremes, horizontal thermal gradients induce a complex flow pattern. In the plane parallel to the tilt axis, the flow pattern is symmetrical and opposite in direction from that where the vessel is positioned vertically. The ground-based experiments are sufficient preliminary tests of theory and should be of significant interest regarding vapor deposited films in microgravity.

Frazier, D. O.↗
NASA NTRS2008

Development of a Silicon Carbide Molecular Beam Nozzle for Simulation Planetary Flybys and Low-Earth Orbit

From commercial origins as a molybdenum molecular beam nozzle, a ceramic nozzle of silicon carbide (SiC) was developed for space environment simulation. The nozzle is mechanically stable under extreme conditions of temperature and pressure. A heated, continuous, supersonically-expanded hydrogen beam with a 1% argon seed produced an argon beam component of nearly 4 km/s, with an argon flux exceeding 1x1014 /cm2.s. This nozzle was part of a molecular beam machine used in the Atmospheric Experiments Branch at NASA Goddard Space Flight Center to characterize the performance of the University of Texas at Dallas Ram Wind Sensor (RWS) aboard the Air Force Communications/Navigation Outage Forecasting System (C/NOFS) launched in the Spring of 2008.

Patrick, E. L.↗
NASA NTRS1980

Low speed test of the aft inlet designed for a tandem fan V/STOL nacelle

An approximately .25 scale model of a Tandem Fan nacelle designed for a Type A V/STOL aircraft configuration was tested in a 10-by-10 foot wind tunnel. A 12 inch, tip driven, turbofan simulator was used to provide the suction source for the aft fan inlet. The front fan inlet was faired over for this test entry. Model variables consisted of a long aft inlet cowl, a short aft inlet cowl, a shaft simulator, blow-in door passages and diffuser vortex generators. Inlet pressure recovery, distortion, inlet angle of attack separation limits were evaluated at tunnel velocities from 0 to 240 knots, angles of attack from -10 to 40 degrees and inlet flow rates representative of throat Mach numbers of 0.1 to 0.6. High inlet performance and stable operation was verified at all design forward speed and angle of attack conditions. The short aft inlet configuration provided exceptionally high pressure recovery except at the highest combination of angle of attack and forward speed. The flow quality at the fan face was somewhat degraded by the addition of blow-in door passages to the long aft inlet configuration due to the pressure disturbances generated by the flow entering the diffuser through the auxiliary air passages.

Rhoades, W. W.↗
NASA NTRS2000

Soot Oxidation in Laminar Hydrocarbon/Air Diffusion Flames at Atmospheric Pressure

Soot oxidation was studied experimentally in laminar hydrocarbon/air diffusion flames at atmospheric pressure. Measurements were carried out along the axes of round jets burning in coflowing air considering acetylene, ethylene, proplyene and propane as fuels. Measurements were limited to the initial stages of soot oxidation (carbon consumption less than 70%) where soot oxidation mainly occurs at the surface of primary soot particles. The following properties were measured as a function of distance above the burner exit: soot concentrations by deconvoluted laser extinction, soot temperatures by deconvoluted multiline emission, soot structure by thermophoretic sampling and analysis using Transmission Electron Microscopy (TEM), concentrations of stable major gas species (N2, H2O, H2, 02, CO, CO2, CH4, C2H2, C2H4, C2H6, C3H6, and C3H8) by sampling and gas chromatography, concentrations of some radical species (H, OH, O) by the deconvoluted Li/LiOH atomic absorption technique and flow velocities by laser velocimetry. It was found that soot surface oxidation rates are not particularly affected by fuel type for laminar diffusion flames and are described reasonably well by the OH surface oxidation mechanism with a collision efficiency of 0.10, (standard deviation of 0.07) with no significant effect of fuel type in this behavior; these findings are in good agreement with the classical laminar premixed flame measurements of Neoh et al. Finally, direct rates of surface oxidation by O2 were small compared to OH oxidation for present conditions, based on estimated O2 oxidation rates due to Nagle and Strickland-Constable, because soot oxidation was completed near the flame sheet where O2 concentrations were less than 1.2% by volume.

Xu, F.↗
NASA NTRS2001

Soot Oxidation in Hydrocarbon/Air Diffusion Flames at Atmospheric Pressure

Soot oxidation was studied experimentally in laminar hydrocarbon/air diffusion flames at atmospheric pressure. Measurements were carried out along the axes of round jets burning in coflowing air considering acetylene, ethylene, propylene and propane as fuels. Measurements were limited to the initial stages of soot oxidation (carbon consumption less than 70%) where soot oxidation mainly occurs at the surface of primary soot particles. The following properties were measured as a function of distance above the burner exit: soot concentrations by deconvoluted laser extinction, soot temperatures by deconvoluted multiline emission, soot structure by thermophoretic sampling and analysis using Transmission Electron Microscopy (TEM), concentrations of stable major gas species (N2, H2O, H2, O2, CO, CO2, CH4, C2H2,C2H4, C2H6, C3H6, and C3H8) by sampling and gas chromatography, concentrations of some radical species (H, OH, O) by the deconvoluted Li/LiOH atomic absorption technique and flow velocities by laser velocimetry. It was found that soot surface oxidation rates are not particularly affected by fuel type for laminar diffusion flames and are described reasonably well by the OH surface oxidation mechanism with a collision efficiency of 0.10, (standard deviation of 0.07) with no significant effect of fuel type in this behavior; these findings are in good agreement with the classical laminar premixed flame measurements of Neoh et al. Finally, direct rates of surface oxidation by O2 were small compared to OH oxidation for present conditions, based on estimated O2 oxidation rates due to Nagle and Strickland-Constable (1962), because soot oxidation was completed near the flame sheet where O2 concentrations were less than 1.2% by volume.

Xu, F.↗
NASA NTRS2017

Effect of Ram and Zenith Exposure on the Optical Properties of Polymers in Space

The temperature of spacecraft is influenced by the solar absorptance and thermal emittance of the external spacecraft materials. Optical and thermal properties can degrade over time in the harsh low Earth orbital (LEO) space environment where spacecraft external materials are exposed to various forms of radiation, thermal cycling, and atomic oxygen. Therefore, it is important to test the durability of spacecraft materials in the space environment. One objective of the Polymers and Zenith Polymers Experiments was to determine the effect of LEO space exposure on the optical properties of various spacecraft polymers. These experiments were flown as part of the Materials International Space Station Experiment 7 (MISSE 7) mission on the exterior of the International Space Station (ISS) for 1.5 years. Samples were flown in ram, wake or zenith directions, receiving varying amounts of atomic oxygen and solar radiation exposure. Total and diffuse reflectance and transmittance of flight and corresponding control samples were obtained post-flight using a Cary 5000 UV-Vis-NIR Spectrophotometer. Integrated air mass zero solar absorptance (s) of the flight and control samples were computed from the total transmittance and reflectance, and compared. The optical data are compared with similar polymers exposed to space for four years as part of MISSE 2, and with atomic oxygen erosion data, to help understand the degradation of these polymers in the space environment. Results show that prolonged space exposure increases the solar absorptance of some materials. Knowing which polymers remain stable will benefit future spacecraft design.

Yuanchun Li↗
NASA NTRS1973

Throat-bypass bleed systems for increasing the stable airflow range of a Mach 2.50 axisymmetric inlet with 40-percent internal contraction

The results of an experimental investigation to increase the stable airflow range of a super sonic mixed-compression inlet are presented. Various throat-bypass bleeds were located on the inlet cowl. The bleed types were distributed porous normal holes, a forward slanted slot, or distributed educated slots. Large inlet stability margins were obtained with the inlet throat bleed systems if a constant pressure was maintained in the throat-bypass bleed plenum. Stability limits were determined for steady-state and limited transient internal air flow changes. Limited unstart angle-of-attack data are presented.

Sanders, B. W.↗
NASA NTRS1975

Factors affecting the palmitoyl-coenzyme A desaturase of Saccharomyces cerevisiae

The activity and stability of the palmitoyl-coenzyme A (CoA) desaturase complex of Saccharomyces cerevisiae was influenced by several factors. Cells, grown nonaerobically and then incubated with glucose, either in air or under N2, showed a marked increase in desaturase activity. Cycloheximide, added during such incubations, prevented the increase in activity, suggesting de novo synthesis. The stability of the desaturase from cells grown nonaerobically was affected by subsequent treatment of the cells; enzyme from freshly harvested cells, or from cells that were then shaken under nitrogen, readily lost activity upon washing or during density gradient analysis, whereas aerated cells, in the presence or absence of glucose, yielded stable enzyme preparations. The loss of activity in nonaerobic preparations could be reversed by adding soluble supernatant from these homogenates and could be prevented by growing the cells in the presence of palmitoleic acid and ergosterol, but not with several other lipids tested.

Klein, H. P.↗
NASA NTRS1989

A cloud model simulation of space shuttle exhaust clouds in different atmospheric conditions

A three-dimensional cloud model was used to characterize the dominant influence of the environment on the Space Shuttle exhaust cloud. The model was modified to accept the actual heat and moisture from rocket exhausts and deluge water as initial conditions. An upper-air sounding determined the ambient atmosphere in which the cloud could grow. The model was validated by comparing simulated clouds with observed clouds from four actual Shuttle launches. The model successfully produced clouds with dimensions, rise, decay, liquid water contents and vertical motion fields very similar to observed clouds whose dimensions were calculated from 16 mm film frames. Once validated, the model was used in a number of different atmospheric conditions ranging from very unstable to very stable. In moist, unstable atmospheres simulated clouds rose to about 3.5 km in the first 4 to 8 minutes then decayed. Liquid water contents ranged from 0.3 to 1.0 g kg-1 mixing ratios and vertical motions were from 2 to 10 ms-1. An inversion served both to reduce entrainment (and erosion) at the top and to prevent continued cloud rise. Even in the most unstable atmospheres, the ground cloud did not rise beyond 4 km and in stable atmospheres with strong low level inversions the cloud could be trapped below 500 m. Wind shear strongly affected the appearance of both the ground cloud and vertical column cloud. The ambient low-level atmospheric moisture governed the amount of cloud water in model clouds. Some dry atmospheres produced little or no cloud water. One case of a simulated TITAN rocket explosion is also discussed.

Chen, C.↗
NASA NTRS2012

Comparison of Aircraft Models and Integration Schemes for Interval Management in the TRACON

Reusable models of common elements for communication, computation, decision and control in air traffic management are necessary in order to enable simulation, analysis and assurance of emergent properties, such as safety and stability, for a given operational concept. Uncertainties due to faults, such as dropped messages, along with non-linearities and sensor noise are an integral part of these models, and impact emergent system behavior. Flight control algorithms designed using a linearized version of the flight mechanics will exhibit error due to model uncertainty, and may not be stable outside a neighborhood of the given point of linearization. Moreover, the communication mechanism by which the sensed state of an aircraft is fed back to a flight control system (such as an ADS-B message) impacts the overall system behavior; both due to sensor noise as well as dropped messages (vacant samples). Additionally simulation of the flight controller system can exhibit further numerical instability, due to selection of the integration scheme and approximations made in the flight dynamics. We examine the theoretical and numerical stability of a speed controller under the Euler and Runge-Kutta schemes of integration, for the Maintain phase for a Mid-Term (2035-2045) Interval Management (IM) Operational Concept for descent and landing operations. We model uncertainties in communication due to missed ADS-B messages by vacant samples in the integration schemes, and compare the emergent behavior of the system, in terms of stability, via the boundedness of the final system state. Any bound on the errors incurred by these uncertainties will play an essential part in a composable assurance argument required for real-time, flight-deck guidance and control systems,. Thus, we believe that the creation of reusable models, which possess property guarantees, such as safety and stability, is an innovative and essential requirement to assessing the emergent properties of novel airspace concepts of operation.

Neogi, Natasha↗
NASA NTRS1948

Wind-tunnel Investigation of High-lift and Stall-control Devices on a 37 Degree Sweptback Wing of Aspect Ratio 6 at High Reynolds Numbers

Results are presented of an investigation in the Langley 19-foot pressure tunnel of the longitudinal characteristics of a semispan model wing having 37 degrees sweepback of the leading edge, an aspect ratio of 6, and NACA 641-212 airfoil section perpendicular to the 27-percent-chord line. Several types of stall-control devices including extensible round-nose leading-edge flaps, a leading-edge slat, and a drooped leading edge were investigated; partial- and full-span trailing-edge split and double slotted flaps were also tested. In addition, various combinations of the aforementioned leading- and trailing-edge flaps were investigated. The tests covered a range of Reynolds numbers between 2.00 x 10(6) and 9.35 x 10(6). The wing with or without trailing-edge splity of double slotted flap was longitudinally unstable near maximum lift due to tip stalling. The addition of an outboard half-span leading-edge flap or a leading-edge slat to the plain wing or wing with inboard half-span split flaps eliminated tip stalling and resulted in stable moment variations at the stall. The drooped leading edge, on the other hand, was only effective when used in conjunction with an upper-surface fence. The combination of an outboard leading-edge device and inboard half-span double slotted flap resulted in an undesirable loop in the pitching-moment curve near maximum lift in spite of an inboard stall. The loop is attributed to the section characteristics of the double slotted flap. Air-flow surveys behind the wing indicated that a suitably placed horizontal tail would eliminate the loop in the moment curve.

Koven, William↗
NASA NTRS2005

Cost-Cutting Powdered Lubricant

Scientists at NASA's Glenn Research Center developed a high-temperature, solid lubricant coating material that is saving the manufacturing industry millions of dollars. The material came out of 3 decades of tribological research, work studying high-temperature friction, lubrication, and the wearing of interacting surfaces that are in relative motion. It was developed as a shaft coating deposited by thermal spraying to protect foil air bearings used in oil-free turbomachinery, like gas turbines, and is meant to be part of a larger project: an oil-free aircraft engine capable of operating at high temperatures with increased reliability, lowered weight, reduced maintenance requirements, and increased power. This advanced coating, PS300, is a self-lubricating bearing material containing chromium oxide, with additions of a low-temperature start up lubricant (silver) and a high-temperature lubricant, making it remarkably stable at high temperatures, and better suited than previously available materials for high-stress conditions. It improves efficiency, lowers friction, reduces emissions, and has been used by NASA in advanced aeropropulsion engines, refrigeration compressors, turbochargers, and hybrid electrical turbogenerators. PS300 is ideal in any application where lowered weight and reduced maintenance are desired, and high-temperature uses and heavy operating speeds are expected. It has notable uses for the Space Agency, but it has even further-reaching potential for the industrial realm.

Source record↗
NASA NTRS2016

Predictive Evaluations of Oxygen-Rich Hydrocarbon Combustion Gas-Centered Swirl Coaxial Injectors using a Flamelet-Based 3-D CFD Simulation Approach

NASA Marshall Space Flight Center (MSFC) has embarked upon a joint project with the Air Force to improve the state-of-the-art of space application combustion device design and operational understanding. One goal of the project is to design, build and hot-fire test a 40,000 pound-thrust Oxygen/Rocket Propellant-2 (RP-2) Oxygen-Rich staged engine at MSFC. The overall project goals afford the opportunity to test multiple different injector designs and experimentally evaluate the any effect on the engine performance and combustion dynamics. To maximize the available test resources and benefits, pre-test, combusting flow, Computational Fluid Dynamics (CFD) analysis was performed on the individual injectors to guide the design. The results of the CFD analysis were used to design the injectors for specific, targeted fluid dynamic features and the analysis results also provided some predictive input for acoustic and thermal analysis of the main Thrust Chamber Assembly (TCA). MSFC has developed and demonstrated the ability to utilize a computationally efficient, flamelet-based combustion model to guide the pre-test design of single-element Gas Centered Swirl Coaxial (GCSC) injectors. Previous, Oxygen/RP-2 simulation models utilizing the Loci-STREAM flow solver, were validated using single injector test data from the EC-1 Air Force test facility. The simulation effort herein is an extension of the validated, CFD driven, single-injector design approach applied to single injectors which will be part of a larger engine array. Time-accurate, Three-Dimensional, CFD simulations were performed for five different classes of injector geometries. Simulations were performed to guide the design of the injector to achieve a variety of intended performance goals. For example, two GCSC injectors were designed to achieve stable hydrodynamic behavior of the propellant circuits while providing the largest thermal margin possible within the design envelope. While another injector was designed to purposefully create a hydrodynamic instability in the fuel supply circuit as predicted by the CFD analysis. Future multi-injector analysis and testing will indicate what if any changes occur in the predicted behavior for the single-element injector when the same injector geometry is placed in a multi-element array.

Richardson, Brian R.↗
NASA NTRS1985

Participation of Ethylene in Two Modes of Gravistimulation of Shoots

In order to elucidate the role of ehtylene in gravitropism, detailed time courses for ethylene production in horizontal and upright plants were measured. Tomato and pea were chosen as examples of plants which exhibit different patterns of gravitropic curvature. Tomato seedlings were placed in gas-tight lucite boxes from which air was sampled and analyzed for ethylene. During the first 2 min interval after one set of plants was turned horizontal ethylene production was double the baseline. Similarly, plants rotated 3 rpm about a vertical axis transiently doubled ethylene production when the axis was shifted 90 deg. In order to clarify the role of this 2-min burst, the effect of exogenous ethylene was studied. In peas, epicotyls were excised, equilibrated until wound ethylene had subsided to a low stable level, and ethylene production was measured in vertical and horizontal segments. As for tomatoes, excised pea epicotyls increased their rate of ethylene production during the first 2 min of gravistimulation. Also, very low concentrations of exogenous ethylene slightly enhance curvature. On the other hand, higher levels of ethylene and 1-aminocyclopropane-1-carboxylic acid (ACC) inhibit overall curvature.

Harrison, M.↗
NASA NTRS1985

Direct coupling of microbore HPLC columns to MS systems

A detailed investigation using electron microscopy was conducted which examined the conditions of materials used in the construction of stable, high performance microbore liquid chromatography (LC) columns. Small details proved to be important. The effects of temperature on the elution of several homologous series used as probe compounds was examined in reverse phase systems. They showed that accessible temperature changes provide roughly half the increase in solvent strength that would be obtained going from a 100% aqueous to a 100% organic mobile phase, which is sufficient to warrant their use in many analyses requiring the use of gradients. Air circulation temperature control systems provide the easiest means of obtaining rapid, wide range changes in column temperature. However, slow heat transfer from the gas leads to thermal nonuniformity in the column and a decrease in resolution as the temperature program progresses.

Mcnair, H. M.↗